[CFE] Use Fasta diagnostics in constant evaluator.

Comments

[CFE] Use Fasta diagnostics in constant evaluator.
The constant evaluator now generates all errors as Fasta diagnostic
messages. The ErrorReporter is simplified to just accept a diagnostic
message, or a notification that the constant evaluator encountered an
invalid expression (presumably put there due to an earlier error).
Also, the flow of control between the error reporter and the internal
abort exceptions is reversed, so the error reporter is now called as a
result of an abort exception being caught by the evaluate method.
Reland of https://dart-review.googlesource.com/c/sdk/+/96300
Change-Id: I7d32b6e98962b6ee781a6c96b593b00ee7fd8a89
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/97225
Commit-Queue: Aske Simon Christensen <askesc@google.com>
Reviewed-by: Kevin Millikin <kmillikin@google.com>